Causes and Classifications

The causes of PAH.

Doctors use the World Health Organization (WHO) system to divide the various types of pulmonary hypertension (PH) into groups. Pulmonary arterial hypertension (PAH) makes up 1 group, referred to as WHO Group 1.

The cause of PAH (WHO Group 1) may be one of the following:

  • Family history of PAH (familial or heritable PAH)
  • Congenital heart disease
  • HIV
  • Certain prescription diet medications such as fenfluramine and dexfenfluramine
  • Certain illegal drugs such as cocaine, amphetamines, and methamphetamines
  • Connective tissue diseases, such as scleroderma
  • Liver disease

However, sometimes no cause can be identified. This type of PAH is called idiopathic PAH. Use the doctor discussion guide to help you learn more about your condition and make the most of your office visits.

Classifying your PAH.

The 5 types of PAH (WHO Group 1) are as follows:

  • Primary or idiopathic PAH. PAH that has no known cause
  • Familial or heritable PAH. PAH that is inherited (passed from parents to children through the genes) or caused by a gene mutation
  • PAH associated with risk factors. PAH associated with use of various drugs or exposure to certain chemicals
  • Associated PAH (APAH). PAH associated with a known, underlying disease or condition, such as
    • Connective tissue diseases (including scleroderma, CREST syndrome, and lupus)
    • HIV infection
    • Portopulmonary hypertension (a type of PAH caused by complications from liver disease)
    • Congenital heart disease (heart disease present at birth)
    • Schistosomiasis (a disease caused by a parasitic worm)
    • Chronic hemolytic anemia (a condition in which there are not enough red blood cells in the body)
  • PAH caused by a condition that affects the veins and blood vessels of the lungs